The recent integration increase of semiconductor devices causes an operation defect of semiconductor devices due to a minute defect that was not such a serious problem in the past, but has a very bad influence upon reliability of the semiconductor devices with a high degree of integration. Defects generated in semiconductor device manufacturing processes may be, for example, foreign particles, a void, dislocation, a stacking fault, an interface fault and the like.
Generally, a surface fault is inspected and measured before or after unit processes of a semiconductor device are performed. A research and development for surface inspection apparatuses to rapidly and precisely detect defects has been actively progressing. It can be understood that the reliability of semiconductor devices depends upon the accurate performance of such surface inspection apparatuses.
Most surface inspection apparatuses employ a bright field optical system for acquiring an image from light reflected from the wafer surface by directing light of a high illumination onto the wafer surface. The bright field optical system uses the reflected light to reproduce an image of the surface. Meanwhile, when employing a dark field optical system using light scattered from defects it is difficult to reproduce an actual image of the wafer surface. Thus, the bright field optical system may be the best way to detect defects on the wafer surface on which various kinds of patterns are formed.
The surface inspection apparatus employing the bright field optical system performs a line scan for a wafer surface by using an image acquisition system, such as a CCD (Charge-coupled device) or TDI (Time Delay Inspection) sensor, so as to detect defects present on an entire face of the wafer. A wafer surface defect detection using such surface inspection apparatus is performed by selecting and sampling a selected area, except for a given portion according to a given skip rule. This is why a defect detection time is long when performing a precise defect inspection for an entire face of a wafer using the image acquisition system of high sensitivity. Thus, a testing throughput decreases.
For example, the TDI sensor uses a swath sampling with a constant scan line interval. A swath sampling of about 25% for the entire face of a wafer is performed according to a skip rule, thereby shortening the defection detection time and thereby increasing a testing throughput.
In the surface inspection apparatus and method described above, however, a throughput can be just enhanced by reducing a scan measurement area when applying a given skip rule, such as swath sampling, but a large amount of defects cannot be detected by an increased skip rule and, thus, a reliability of the defect detection decreases.
Furthermore, when a large amount of defects concentrated mainly on a partial surface, such as an edge portion of a wafer cannot be completely detected, errors in semiconductor manufacturing processes occur and, thus, a production yield decreases.